It is a continuing problem in log yards that accumulated log debris becomes mingled with rock and soil, forming an aggregate. Attempts by yard owners to stabilize the wet aggregate to improve traction for equipment results in additional gravel and rock being added.
Decomposition of the wood portion of the aggregate results in the production of noxious by-products that are more frequently being viewed as environmentally unacceptable.
The aggregate is essentially a combination of three particulate components, namely high density mineral particles, low density wood particles, and relatively fine soil particles.
Log yard operators have, to date, sought methods to treat the mixtures, with unsatisfactory results.
Techniques tried have included flotation for separating the wood from the mineral portion, expecting the wood to readily float free. This approach has been unsuccessful due to the large fraction of wood that is waterlogged and will not float. Additionally, the water used for flotation becomes contaminated and becomes a further liability.
Air separation or elutriation techniques have also been attempted in the past. The difficulty with typical elutriation techniques is that they are as likely to lift and separate out small particles of high density rock as they are to separate out larger pieces of low density wood. The product still remains a mixture of mineral and wood particles.
Top soil can be a large fraction of these waste aggregates and is a valuable commodity which has been generally unrecoverable to date.
With the foregoing background in mind, it was the objective of the present invention to provide an apparatus and a method whereby soils and light density material, such as wood, may be successfully separated from higher density material, such as rock, regardless of the variation of sizing in the original aggregate.